The present disclosure relates to methods for use in subterranean formations, and more specifically, methods for determining acidizing fluid injection rates for stimulation of a subterranean formation.
Hydrocarbons, such as oil and gas, are commonly obtained from subterranean formations that may be located onshore or offshore. The development of subterranean operations and the processes involved in removing hydrocarbons from a subterranean formation typically involve a number of different steps such as, for example, drilling a wellbore at a desired well site, treating the wellbore to optimize production of hydrocarbons, and performing the necessary steps to produce and process the hydrocarbons from the subterranean formation.
Acid treatments are used to stimulate and increase the production of hydrocarbons in a subterranean formation comprising acid-soluble components, such as those present in carbonate and sandstone formations. This is commonly referred to as acidizing. One such aqueous acid treatment, referred to as “matrix acidizing,” involves the introduction of an acid into a subterranean formation under pressure so that the acid flows through the pore spaces of the formation. The acid of the aqueous acid treatment reacts with acid soluble materials contained in the formation to increase the size of the pore spaces and increase the permeability of the formation.
In carbonate formations, matrix acidizing creates conductive flow channels known as wormholes that bypass the damage in the formation. The wormholes are formed when the matrix of the porous and permeable rock is dissolved by reactive fluids. The fluid injection rate is an especially important consideration in developing deep penetrating wormholes. When the injection rate is too low, the acidizing fluid may only dissolve the rock in the vicinity of the wellbore and wormholes may not form. When the injection rate is too high, the treatment may form thick and shallow wormholes that do not penetrate deep enough into the formation.
Traditionally, treatment fluids associated with acid treatments such as matrix-acidizing are injected at the maximum pressure differential and injection rate (“MAPDIR”). While this injection rate is simple, it uses large volumes of acid, is limited by pump and tubing capacity, and may not achieve optimal stimulation of the subterranean formation.
While embodiments of this disclosure have been depicted, such embodiments do not imply a limitation on the disclosure, and no such limitation should be inferred. The subject matter disclosed is capable of considerable modification, alteration, and equivalents in form and function, as will occur to those skilled in the pertinent art and having the benefit of this disclosure. The depicted and described embodiments of this disclosure are examples only, and not exhaustive of the scope of the disclosure.